Abstract

Optimization of the stress transfer capability of the fibre-matrix interphase region is critical to achieving the required performance level in thermoplastic matrix composites. Despite the ever increasing diversity of the reinforcements available for polymer composites, glass fibres still account for 95% of fibre reinforcements used in the composites industry, primarily due to of their highly attractive performance/price ratio. Due to its initial location on the glass fibre surface, the sizing layer is an important component in the formation and properties of the composite interphase. A large proportion of the research published on interphase optimization in these materials has focussed on the role of the organosilane coupling agents which are almost universally present in glass fibre sizing. Perhaps due to their common name of "coupling agents", perhaps due to their reactive nature or even perhaps due to the early focus of composites research on chemically reactive thermosetting matrices, there exists a dominant mindset in the composites research community to approach the interphase from a chemical bonding viewpoint. While this approach may very well be justified in thermosetting matrix composites it is not at all clear that this is also the case for reinforced thermoplastics, in particular for the commercially important polyolefin based composites.